Power Supply Device For Driving An Amplifier

ABSTRACT

A power supply device for driving first and second amplifiers includes a first power generator, a second power generator, a charge pump and a control unit. The first power generator provides a first voltage for first power reception ends of the first and second amplifiers. The second power generator provides a second voltage. The charge pump is coupled between the second power generator and a second power reception end of the first amplifier and between the second power generator and a second power reception end of the second amplifier, and is used for generating a third voltage for the first and second amplifiers according to the second voltage. The control unit is coupled to the second power generator and is used for controlling the second power generator, so as to adjust the second voltage to make the third voltage equal to a multiple of the first voltage.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a division of application Ser. No. 11/610,483, filed Dec. 13,2006, which claims the benefit of U.S. Provisional Application No.60/822,084, filed Aug. 11, 2006, the entirety of which is incorporatedby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power supply device for driving anamplifier, and more particularly, to a power supply device capable ofreducing power consumption of an amplifier and enlarging an output rangeof the amplifier.

2. Description of the Prior Art

An amplifier is an electronic device used in a variety of electronicproducts, which can amplify signal amplitudes. The amplifier appears inmany types and structures, which can be simply composed of a bipolarjunction transistor (BJT) or a metal oxide semiconductor (MOS)transistor, or be integrated by complicated circuits such as OP 741.

The amplifier is widely used in many applications. For example, U.S.Pat. No. 7,061,327 discloses a headset using a single voltage supply todrive an operational amplifier of the headset via a charge pump.Furthermore, U.S. Pat. No. 5,289,137 discloses an integrated circuitusing a single power supply and a charge pump for driving an operationalamplifier. Both of the U.S. Pat. No. 7,061,327 and No. 5,289,137 usesingle power supplies with charge pumps for driving the amplifier.However, shortcomings of these two patents are power consumption andrestriction of output ranges. The details are described as bellows.Please refer to FIG. 1, which reveals a schematic diagram of signalscorresponding to an amplifier in FIG. 4 of the U.S. Pat. No. 7,061,327.Voltages V_(DD) and V_(SS) respectively represent a positive voltage anda negative voltage for driving the amplifier. Since the U.S. Pat. No.7,061,327 uses single power supply with a charge pump, the voltageV_(DD) can keep a relation by V_(SS)=−V_(DD). In addition, the chargepump is substantially composed of capacitors and thereby, generates theVoltage V_(SS) via charging and discharging of the capacitors. Underthis circumstance, the voltage V_(SS) performs as an unstable linearcurve rippling as the capacitors are charged and discharged. Sinceamplitudes of output signals of the amplifier must be restricted betweenthe voltages V_(DD) and V_(SS), negative amplitude of the amplifier maybe curtailed as a variation range of the voltage V_(SS) becomes large.In order to solve the problem, the prior art can increase the voltageV_(DD) so that the output range of the amplifier can be enlarged, orincrease capacitance of the capacitors in the charge pump. However,increasing the voltage V_(DD) represents increasing power consumption,while increasing capacitance of the capacitors in the charge pumprepresents increasing the capacitor size.

Therefore, using a single power supply with a charge pump for driving anamplifier results in a restriction of an output range of the amplifier,and power consumption cannot be efficiently reduced. Besides, if asingle power supply is used for driving multiple amplifiers, currentvariation produced by switching transistors of a certain amplifier maycause malfunction of the power supply, and reduces system efficiency.

SUMMARY OF THE INVENTION

It is therefore a primary objective of the claimed invention to providea power supply device for driving an amplifier.

The present invention discloses a power supply device for driving afirst amplifier and a second amplifier, which comprises a first powergenerator for providing a first voltage for a first power reception endof the first amplifier and a first power reception end of the secondamplifier, a second power generator for providing a second voltage, acharge pump coupled between the second power generator and a secondpower reception end of the first amplifier and between the second powergenerator and a second power reception end of the second amplifier, forgenerating a third voltage for the first amplifier and the secondamplifier according to the second voltage, and a control unit coupled tothe second power generator, for controlling the second power generator,so as to adjust the second voltage to make the third voltage equal to amultiple of the first voltage.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a schematic diagram of signals corresponding to anamplifier according to a FIG. 4 of the U.S. Pat. No. 7,061,327.

FIG. 2 depicts a schematic diagram of a power supply device for drivingan amplifier according to a first embodiment of the present invention.

FIG. 3 depicts a schematic diagram of signal waveforms corresponding tothe amplifier in FIG. 2 in a power saving mode.

FIG. 4 depicts a schematic diagram of signal waveforms corresponding tothe amplifier in FIG. 2 in a normal mode.

FIG. 5 depicts a schematic diagram of the power supply device fordriving two amplifiers in FIG. 2.

FIG. 6 depicts a schematic diagram of a power supply device for drivingan amplifier according to a second embodiment of the present invention.

DETAILED DESCRIPTION

Please refer to FIG. 2, which is a schematic diagram of a power supplydevice 10 for driving an amplifier 12 according to an embodiment of thepresent invention. The amplifier 12 receives driving power through apositive power reception end 120 and a negative power reception end 122,amplifies a signal V_(IN) received by a signal reception end 124, andoutputs a signal V_(OUT) from a signal output end 126. The power supplydevice 10 includes a first power generator 100, a second power generator102, a charge pump 104, and a control unit 106. The first powergenerator 100 and the second power generator 102 generate voltagesCV_(DD) and CV_(CC) for a positive power reception end 120 of theamplifier 12 and the charge pump 104. The charge pump 104 converts thevoltage CV_(CC) provided by the second power generator 102 into anegative voltage CV_(SS), CV_(SS)=(−n2)×CV_(CC), and outputs the voltageCV_(SS) to the negative power reception end 122 of the amplifier 12.Thus, positive and negative powers driving the amplifier 12 are providedby different power generators. The control unit 106 controls the voltageCV_(CC) of the second power generator 102, so as to adjust the voltageCV_(SS) to make the voltage CV_(DD) equal to a multiple of the voltageCV_(SS), or CV_(SS)=(−n)×CV_(DD).

Therefore, in the power supply device 10, levels of positive andnegative powers of the amplifier 12 may be different for applying todifferent situations. For example, please refer to FIG. 3 and FIG. 4.FIG. 3 is a schematic diagram of signal waveforms corresponding to theamplifier 12 in a condition of n=0.5, while FIG. 4 is a schematicdiagram of signal waveforms corresponding to the amplifier 12 in acondition of n=1.5. In FIG. 3, the output voltage V_(OUT) of theamplifier 12 has a small amplitude when operating in a power savingmode, such as an idle mode, so that setting n smaller than 1 can reducequiescent current and power consumption. On the contrary, in FIG. 4, theoutput voltage V_(OUT) of the amplifier 12 has a greater amplitude whenoperating in a normal mode, so that n can be set larger than 1. In thisway, even if the voltage CV_(SS) varies with charging and dischargingcapacitors of the charge pump 104, signals outputted from the amplifier12 can be prevented from being curtailed since the voltage CV_(SS) is1.5 times the voltage CV_(DD), meaning that the amplifier 12 has a wideroutput range in the negative polarity. Thus, the capacitors in thecharge pump 104 can be replaced with capacitors of less capacitance, sothat a size of the charge pump 104 can be reduced.

Note that, the power supply device 10 shown in FIG. 2 is an exemplaryembodiment of the present invention, and those skills in the art canmake modification, such as driving a plurality of amplifiers, not justone. Please refer to FIG. 5, which is a schematic diagram of the powersupply device 10 for driving amplifiers 500, 502 according to thepresent invention. The amplifiers 500, 502 receive driving power frompositive reception ends 520, 528 and negative reception ends 522, 530,amplify signals V_(IN) 1, V_(IN) 2 received from signal reception ends524, 532, and then output signals V_(OUT) 1, V_(OUT) 2 to a load circuit504, such as a stereo headphone or a loudspeaker, through signal outputends 526, 534.

In addition, the present invention can also accomplish the sameperformance by one power generator. Please refer to FIG. 6, which is aschematic diagram of a power supply device 60 for driving an amplifier62 according to a second embodiment of the present invention. Theamplifier 62 receives driving power from a positive power reception end620 and a negative power reception end 622, amplifies a signal V_(IN)received by a signal reception end 624, and outputs a signal V_(OUT)through a signal output end 626. The power supply device 60 includes apower generator 600, a power conversion unit 602, a charge pump 604 anda control unit 606. The power generator 600 provides a voltage CV_(DD)for a positive power reception end 620 of the amplifier 62 and the powerconversion unit 602. The power conversion unit 602 converts the voltageCV_(DD) into a voltage CV_(CC) and outputs the voltage CV_(CC) to thecharge pump 604. The charge pump 604 converts the voltage CV_(CC)provided by the power conversion unit 602 into a negative voltageCV_(SS) ( CV_(SS)=(−n2)×CV_(CC)) and outputs the voltage CV_(SS) to thenegative power reception end 622 of the amplifier 62. Besides, thecontrol unit 606 controls the voltage CV_(CC) of the power conversionunit 602, so as to adjust the voltage CV_(SS) to make the voltageCV_(DD) equal to a multiple of the voltage CV_(SS), orCV_(SS)=(−n)×CV_(DD).

Therefore, in the power supply device 60, levels of positive andnegative powers of the amplifier 62 may be different for applying todifferent situations. In a power saving mode (as shown in FIG. 3 ), theoutput voltage VOUT of the amplifier 62 has a small amplitude, so thatsetting n smaller than 1 can reduce quiescent current to reduce powerconsumption. On the contrary, in a normal mode (as shown in FIG. 4), theoutput voltage V_(OUT) of the amplifier 62 has a greater amplitude, sothat n can be set larger than 1. In this way, even if the voltageCV_(SS) varies with charging and discharging capacitors of the chargepump 604, signals outputted from the amplifier 62 can be prevented frombeing curtailed since the voltage CV_(SS) is 1.5 times the voltageCV_(DD), meaning that the amplifier 62 has a wider output range in thenegative polarity. Thus, the capacitors in the charge pump 604 can bereplaced with capacitors of less capacitance, so that a size of thecharge pump 604 can be reduced.

In summary, in the present invention power supply device, levels of thepositive and negative powers of the amplifier can be different. In thepower saving mode, the present invention can set n smaller than 1 forreducing quiescent current and saving power. In the normal mode, thepresent invention can set n larger than 1, so that the amplifier has awider output range in the negative polarity. Under this circumstance,the capacitors in the charge pump can be replaced by capacitors of lesscapacitance, so that the size of the charge pump can be further reduced.In addition, due to two power generators driving multiple amplifiers,the present invention can prevent current variation generated byswitching transistors from affecting system operations.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

1. A power supply device for driving a first amplifier and a secondamplifier comprising: a first power generator for providing a firstvoltage for a first power reception end of the first amplifier and afirst power reception end of the second amplifier; a second powergenerator for providing a second voltage; a charge pump coupled betweenthe second power generator and a second power reception end of the firstamplifier and between the second power generator and a second powerreception end of the second amplifier, for generating a third voltagefor the first amplifier and the second amplifier according to the secondvoltage; and a control unit coupled to the second power generator, forcontrolling the second power generator, so as to adjust the secondvoltage to make the third voltage equal to a multiple of the firstvoltage.
 2. The power supply device of claim 1, wherein the firstamplifier and the second amplifier are used for amplifying audiosignals.
 3. The power supply device of claim 1, wherein the firstamplifier and the second amplifier are operational amplifiers.
 4. Thepower supply device of claim 1, wherein the control unit controls thesecond power generator to make the third voltage smaller than the firstvoltage when both the first amplifier and the second amplifier operatein a power saving mode.
 5. The power supply device of claim 1, whereinthe control unit controls the second power generator to make the thirdvoltage greater than the first voltage when both the first amplifier andthe second amplifier operate in a wide output range mode.